As a frequency of use of wireless communications of a user increases and the number of categories of services using wireless communications increases, the need for support of a high data rate and high quality of service (QoS) to a user who moves at high speed unlike in a conventional situation has been on the rise. For example, when a plurality of users who use public transportation want to watch multimedia during the ride or a plurality of passengers who ride a personal vehicle driving on a highway use different wireless communication services, a mobile communication system needs to support a high-quality wireless service to the above users.
The service is a new model that has not been present in a conventional wireless communication service model, and in order to support the service, there is a need to design a new system for innovatively enhancing a mobile communication network or embodying the mobile communication network rather than affecting a network infrastructure. As one of solutions for this, a vehicular multiple input multiple output (MIMO) system for installing a large size antenna array in a vehicle so as to allow the vehicle to receive a high-quality service also in a high speed movement situation via a large array gain and relaying received data by a central unit of the vehicle to a riding passenger has been considered.
When a large antenna array is installed outside a vehicle and wireless communications between a base station and a passenger in a vehicle is relayed through the large antenna array, degradation in communication performance may be prevented due to penetration loss with an average value of about 20 dB, a large array gain may be ensured due to use of many reception (Rx) antennas compared with a personal portable communication devices, and a distance between the Rx antennas may be easily ensured so as to easily ensure Rx diversity. Accordingly, the vehicular MIMO may provide an excellent communication service compared with a personal portable device without additional investment of infrastructures.
However, despite this advantage, there has been no example of a large antenna array installed in a vehicle. A vehicle is significantly expensive equipment compared with a conventional personal portable communication device and is not easy to improve and upgrade. In addition, the vehicle is equipment that satisfies as many as possible requirements such as design concept and an aeromechanical structure as well as communication performance, and thus it is not easy to install a large antenna array that limits aesthetic/aeromechanic vehicle design. In order to remove visual inconvenience of existing antennas, vehicle manufacturers have used a combination antenna with degraded performance compared with a single antenna.
In order to resolve spatial restriction of a large antenna array, installment of a distributed antenna array system for embodying an arrayed antenna system through a plurality of arrays instead of a single array in a vehicle has been considered.